Seal for fluid containers



Oct. 16, 1951 E. T. ARMSTRONG SEAL FOR FLUID CONTAINERS 2 SHEETS-SHEET 1Filed April 9, 1947 Fmmimvvr m W y 1. a

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Oct. 16, 1951 E. T. ARMSTRONG SEAL FOR FLUID CONTAINERS 2 SHEETS-SHEET 2Filed April 9, 1947 ,dwm h M m m m Patented Oct. 16, 1951 SEAL FOR FLUIDCONTAINERS Edward T. Armstrong, Columbus, Ohio, assignor, by mesneassignments, to Stacey Brothers Gas Construction Company, Cincinnati,Ohio, a

corporation of Ohio Application April 9, 1947, Serial No. 740,368

16 Claims.

This invention relates to fluid storage reservoirs of the class having afloating, vertically translatable piston confined within a cylindricalreservoir, which piston functions as a movable top closure to confinethe fluid in the reservoir.

Such reservoirs include gas holders of the type wherein the gas istrapped in the reservoir by the piston which, by virtue of its effectiveweight, maintains the gas under pressure, as well as volatile liquidcontainers with floating roofs. The present invention is directed toimprovements in the sealing apparatus of the piston by means of which agas-tight seal is established mechanical- -ly between the piston and thereservoir or shell.

It has been the practice to utilize, for this purpose, one or moredilatable packing rings forming a part of the piston to establish amechanical seal with the shell. A series of levers. or other means,carried by the piston at spaced intervals, expands the ring outwardlyagainst the shell to establish a seal, in the presence of a suitablelubricant. The United States Patent No. 2,371,966 of H. H. Liese et al.,granted March 20, 1945, is representative of this structure. An evenearlier example of this general type of holder may be found in thepatent to Einbeck et al., 1,924,029, granted August 22, 1933.

The present improvements are directed to this type of dry seal holder asdistinguished from the liquid seal type exemplified in the patents to K.Jagschitz, No. 1,275,696, granted August 13, 1918, and No. 1,481,099granted January 15, 1924.

Th liquid seal type holder essentially constitutes a piston disposedwithin a holder shell and incorporating a trough circumferentiallyarranged and open to the wall surface of the shell. A viscous sealingliquid is carried in the trough, which liquid leaks through the spacebetween the shell and the piston and in so doing seals the pistonrelative to the shell. The liquid trickles down the Wall of the shell toa collecting trough at the bottom and is returned to the top of thepiston by means of an automatic pumping system.

Briefly, it is the concept of the present inventor to provide asimplified piston seal comprised esis supported by a spring loadedsupport member,

the seal being joined to the lower edge of a flexible skirt extendingfrom the piston. The skirt is exposed to the gas trapped under pressurebeneath the piston and, therefore, is responsive to pressure changes tovary the sealing pressure of thering in accordance with gaspressure-changes.

The seal ring may be formed of a continuous plastic extrusion ofU-shaped or other cross section to adapt it to be engaged upon asupporting bar of flat cross section, slotted at intervals to imparttangential flexibility. This bar initially may be straight and uponinstallation be bent to a circular arc conforming to. the cylindricalgas holder shell. Together, the elastic seal ring and flexible supportbar provide a unit of increased flexibility, which accommodates itselfreadily to local or general shell irregularities. Friction is reducedand therefore the piston is more, in its movement, responsive topressure changes and there is less wear.

The support bar is carried by a series of spacing members or stavesextending from the piston in the form of flat, springy plates adjustablymounted and arranged to spring load the flexible support bar at a seriesof points around its periphery. A skirt or apron, of flexible, gasimpermeable material extends continuously around the piston, having oneedge sealed with the piston or deck, and the other edge joined insealing relation with the seal ring. This skirt arrangement permitsexpansive and contractive movements of the seal relative to the pistonto accommodate shell irregularities.

Due to the functional limitations of dry or waterless seals constructedin the past, it has been necessary to provide a shell built with greaterprecision than was necessary for the liquid type seal. Consequently theinitial cost of the holder shell has been greater for a dry seal gasholder. On the other hand, maintenance costs are greater for the liquidseal holder than the dry, by reason of the use of sealing liquids and ofservicing the holder. Performance of the liquid and dry seal holders isapproximately equal if shell diameter, concentricity and verticalalignment of the dry holder shell are held within close limits. Shellfabrication costs, however, increase sharply as the specified tolerancesare reduced.

Primarily it has been the object of the inventor to reduce gas storagecosts by the provision of a dry piston seal of simplified design, havingimproved shell accommodation and characterized by reduced friction andminimized wear to permit its application to holder shells fabricatedaccording to lower cost liquid seal standards; as distinguished from dryseal precision practice.

A more specific object has been to provide a narrow-band continuousflexible dry seal by establishing substantially a line contact with theholder wherein the pressure in the narrow contact area is sufiicient tocompletely prohibit the passage of stored gas despite irregularities inthe shell surface contour and notwithstanding a certain amount of pistontilt.

It has been a further object to provide a continuous elastomeric sealingring reinforced by a more generally flexible flat metal support ring,the elasticity of the sealing ring compensating for local irregularitiesand the metal support ring compensating, by more general deformation, tothe overall deviations and eccentricities of the holder shell, thesealing unit being responsive tovariations in gas pressure to vary itssealing pressure accordingly.

Undue wear of the seal ring is avoided by holding the mechanical orspring loading of the ring to a minimum and supplementing it with gasdeveloped pressure. This is accomplished by the expansible skirt ordiaphragm exposed to the stored gas pressure on one side and to aseparate pressure on the other side. Changes in gas pressure induceproportional variations in seal load due to the eiiect of differentialpressure on the skirt. Thus, the seal load is always maintained at theminimum value required to effect sealing resulting in reduced frictionand seal wear.

The ring, upon which is engaged the elastic seal section, permits theuse of a continuous extruded element of uniform cross-section which maybe produced commercially at low' cost. Adjustable bending means areprovided by means of which the relation between the spring load- .il'lgand gas pressure loading of the seal ring unit may be varied to suit therequired operating conditions.

These and other objects and advantages of the invention not specificallyset forth will be I more fully disclosed with reference to the ac-Figure 1, illustrating the skirt sealing, bead which forms also thefulcrum point for the flat loading springs. 1

Figure 5 is a fragmentary perspective view of a portion of the sealingorganization as viewed from the outside of the piston.

Figure 6 is a fragmentary sectional View similar to Figure l, detailingon an enlarged scale, the adjustable mounting means for the seal ring.

Figure '7 is an enlarged sectional view showing a somewhat modifiedarrangement for attaching the elastic seal and flexible mounting bar tothe piston.

The several views of the drawings are limited to portions of the gasholder sufiicient to illustrate full the environment, construction, and

operation of the improved seal. Generally described, the holder shell isindicated at la, the

pistongenerally at H and the sealing organization generally at l2.

The vertical cylindrical shell or cylinder is fabricated of steel platessuitably joined together, for example by welding or riveting. Thesejoints may be machined or otherwise -dressed topresent a relativelysmooth; even in ternal surface contour. Suitable structural steelbracing is applied to the outside of the shell to stabilize and supportit according to prevailing commercial practice.

The piston H generally comprises a deck l3 formed of steel platessuitably joined together in the form of a dome-like structure. disposedwithin the shell 18. A series of horizontal beams i5 marginally definethe circular contour of the piston, the beams being secured to theunderside of the deck and forming the foundation for a superstructure [6of the piston. A reinforcing structure ll fabricated of structural steelmembers is disposed beneath the deck to reinforce and stiffen it.

In its vertical movements relative to the shell, the piston is guided bythe superstructure to prevent lateral tilting. For this purpose a seriesof circumferentially arranged guide rollers disposed in tiers spaced oneabove the other, is carried by the superstructure. These rollers is arejournalled in brackets"- I9, which brackets are secured upon a series ofvertical I beams 20 rising above the piston and forming a part of thesuperstructure It. The lower ends of I beams 26 are supported upon thehorizontal I beam i5 and have their upper ends secured together b meansof circumferential, horizontally disposed I beams 2|. A bracingstructure 22 extends angularly from the piston deck to the upper ends ofthe vertical I beams to stiffen the superstructure.

By virtue of the guide rollers l8 bearing against and tracking upon thesurface contour of the shell, the superstructure l6 and piston deck iscaused to follow the shell contour and excessive tilting of the pistonrelative to the shell is prevented.

Sealing apparatus [2' for the piston is supported in a substantiallyhorizontal plane primarily from a marginal extension 2% of the pistondeck. For this purpose an angle iron 2'! extends continuously around themarginal edge of extension 26, being secured thereto preferably bywelding to provide a gas-tight connection with the piston deck.Approximately midway of the length of the vertical leg 28 of the angleiron 27, is secured a continuous circumferential channel iron 29 havingseated therein a resilient gasket or bead 3&.

Along the upper portion of leg 28 is located a series of support pins 32upon each of which is hung one of a series of flexible staves 33, thelower ends of which carry the seal member as hereinafter described. Eachstave is controlled individually by an adjusting screw 35 at the upperend of the plate, which screw engages in a nut 36 welded or otherwisesecured to the outside surface of the plate. The opposite end of each ofthe adjustin screws is anchored in an I beam 38 extending around thesuperstructure, the I beam being secured to the upright I beams 20. Eachscrew passes through one of a series of spaced apertures 39 formed in aweb of the I beam 38, the screw including a head 40 bearing against theweb. These screws preferably are of the socket head type having acylindrical outside diameter and an internal hexagonal or fluted bore,adapted to receive an instrumentalit for adjusting them. As viewed inFigures 1 and 6, each stave functions as a lever pivoted upon theannular bead or gasket 30, the screw 35 drawing the upper end inwardlyand bending the lower end outwardly to-expand the seal unit against theholder shell wall surface.

tween the bead and the hangers 33.

Referring to Figures 2 and 3, the piston seal unit consists of arelatively fiat elastic band 43 of U-shaped cross-section, engaged uponand carried by a flexible support bar 44. The support bar in turn issecured to a right-angled end portion 45 formed at the lower end of eachof the respective hangers 33. This attachment is by means of uprightstuds 43 preferably welded upon the horizontal portions 45 and passingthrough apertures 4'! in the support bar 44, at suitable spacing. Nuts48 engaged upon the studs 46 clamp the support bar securely in place onthe hangers.

.Slots 49 are cut into the flat metal support bar 44 from alternatelyopposite side edges to render the plate tangentially and radially flexi-'ble. steel'stock in straight condition, which upon being assembled,follows the circular contour of the holder shell. It is deformablegenerally, that is, it will accommodate itself to general irregularitiesencountered in the surface contour 'of the holder shell, such aseccentricity or general deviations from a plane surface in the verticaldirection. It will not as readily accommodate itself to purely localirregularities encountered in its vertical translation, as will thelocall resilient sealing band 43. I

Sealing band 43 is formed of aflexible material which may be generallycharacterized as a synthetic elastomer, although natural rubber also maybe used. It is formed preferably as a continuous extrusion of relativelyflat configuration, U-shaped in cross-section to provide a pair of limbs50, having a wedge-like solid connecting section 5|, with a roundedsealing edge 52. By virtue of the sealing pressure imposed on thecontact surface, this resilient rounded edge which contacts the shell,is deformed or flattened slightly along its line of contact therewith toform a narrow sealing band, closely embracing and establishing a moreperfect seal with the shell.

As shown in Figures 2 and 3 the band 43 is slipped over the edge of theflat support bar 44 with its limbs 50 disposed on opposite sides of thebar. A series of bolts 54 pass through the limbs and bar, each bolthaving washers 55, one "under the bolt head 56 and the other under thenut 5'1. The lower edge of a flexible skirt or apron 59 is doubled overthe edge of support bar 44 as at 69 to establish a gas-tight joint withthe sealing band 43.

Thus, the doubled over skirt portion 50 is clamped tightly between therespective upper and lower limbs 50 and bar 44, and a double sealestablished between the resilient sealing band 43 and skirt 59. Ifdesired, a sealing coat of cement or the like may be applied in thisarea prior to assembly. It will be understood that the "skirt andsealing band extend continuously around the circumference of the pistonto form an unbroken seal, the adjacent vertical ends of the band andlikewise the skirt being joined together in an appropriate manner.

'From the sealing band the skirt extends horizontally inwardly along theflanged lower end 45 of hangers 33, then rises vertically in contactwith the inside surface of the hangers, to which surface it may becemented or otherwise secured. As shown in Figure 6, the skirt passesover the resilient fulcrum bead 35 and is thus pressed be- In order toinsure a seal between the gasket and the skirt,

* a coating of flexible cement may be applied there- This plate isformed preferably from fiat between. The skirt may terminate at anydesired level above the bead 30, this portion, of-course, being securedto the hangers 33 by a suitable adhesive.

As will be apparent from Figures 1 and 6, the effective portion of theskirt is that area extending between the seal 43 and bead 3|), whicharea is exposed to the gas pressure under the piston and forms in effecta continuation of the piston deck I3.v Gas pressure thus sets up adiaphragm action upon the skirt and hangers, causing the hangers totransmit the gas pressure to the support bar 44 and sealing band 43. Bythis arrangement the spring loading of the bar may be kept at a minimumto avoid unnecessary wear of the seal. This in turn makes the pistonmore responsive to gas pressure changes since it minimizes mechanicalfriction between the shell and seal.

The skirt is preferably made from a fabric cloth having a coating ofplastic material such as neoprene or Vinylite to make it gas-tight.Other commercially available diaphragm materials,'such as rubber coatedfabrics or flexible plastic sheet materials, also may be utilized. Byreason of a slight circumferential expansion required of the skirt, itis of course preferable that the material be slightly elasticcircumferentially. Also, the material is required to be relatively softso as not to affect adversely the function of the sealing apparatus. a

In the vertical translation of the piston relative to the shell, generalshell irregularities encountered by the superstructure guide rollers,are transmitted directly to the piston deck. This tends to cause lateralpiston shift and tilt relative to the shell, which action would tend tocause leakage of gas past the sealing band 43. Also, this tends toproduce further tilt due to increased loading induced at a pointdiametrically opposite the leak. However, the flexible skirt and hangerspermit the piston to 'tilt or shift laterally as a' unit relativeto thesealing apparatus without causing leakage. There is essentially nochange in the seal contact pressure so that leakage is avoided andfurther tilting due to variation in seal friction is eliminated.

The design of the seal support bar 44 combined with the independentlyadjustable resilient staves 33 result in increased accommodation to theshell and a minimum of friction between the shell and the sealing band.As viewed in Figure 3, the support bar 44 is spring loaded at equallyspaced intervals around its circumference. The design of the bar is suchthat it distributes uniformly the load between the spring hangers,resulting in a'constant uniform pressure about the circumference andpermits a minimum number of hangers to be used. Beinggenerallydeformable, it is free to deflect and conform to general devia- 'tionsin the shell structure while the more resilient sealing band 43 is freeto accommodate itself to relatively minute inaccuracies in the surfacecontour of the shell. By reason of the relatively narrow contact areaestablished with the shell by the seal band, the sealing load isconcentrated and higher seal contact pressures are attained with reducedseal loads, thereby reduc- '.are greatlylengthened.

Lubrication tominimize friction and wear he'- Supply means for thelubricant is not illustrated since this portion of the structure is nota part of the present invention. While the seal disclosed herein may belubricated by heavy greases'of the type previously used in this type ofwaterless gas holder, the lubrication necessary may also be accomplishedby the use of more fluid lubricants such as mineral oil or antifreezesolutions of the glycerine, or ethylene glycols type.

As shown in Figure 7 a somewhat modified mounting is provided for thesupport bar and sealing band. In this instance the spacing memher orstave 33 has at its lower end, an angle member 65 secured theretopreferably by welding. This member supplants the horizontal flange 45previously described and provides a mounting surface for the support barin place of the flange. A bolt and nut 66 extends through the lowerflange B'lof the support member, the nut engaging the top surface of theflange to secure the support bar firmly in position.

Referring to Figure 6 of the drawings, the sealing load is developed bydrawing the upper end of the flexible hanger inwardly toward the centerof'the piston, the position of maximum pressure being illustrated indot-dash lines. By virtue of the lever action of the hangers pivotedupon the bead 3B, the pressure exerted against the seal ring 43 may begreater than that developed at the upper end of the hanger. This ofcourse facilitates adjustment of the hangers and permits the use ofrelatively simple elements for this purpose. The resiliency of head 30additionally supplements the spring action of the hangers. It will beapparent that the leverage of the hangers may be increased or decreasedto suit particular conditions by changing the location of the fulcrumbead 30 relative to the seal.

It is desirable to adjust all of the hangers surrounding the piston to aposition of approximately equal pressure so that the seal is equallyloaded around its entire circumference.

When this ideal condition prevails, the piston is in a balancedcondition with respect to the seal, there .being a minimized variationin seal contact pressure from point to point about the periphery andconsequently friction of the seal and wear of the seal is minimized.This uniformity of loading reduces the effect of frictional seal forcesin inducing tilting of the piston. It will be apparent, of course, thatlocal deviations in the shell contour will cause localized springing ofthe seal ring and hangers in that area, but due to the generalflexibility of the supporting bar, such deflections are localized to thearea affected. Therefore, the tendency to deflect the ring bod- .ily ina lateral direction is kept to a minimum.

no such flat face exists and the ring will simply expand to compensatefor the irregularity. This condition obtains since the cylindricalgeometry of the seal contact face is insensitive to angular deviationwithin a-fairly large range of angular tilt. r

The novel principles and structural improvements embodied in the sealfor the fluid storage reservoir specifically disclosed herein aresusceptible to individual as well as joint utilization, not only inreservoirs which are geometrically circular, as disclosed, but alsowhich are approximately circular, polygonal, for instance. As disclosed,two superimposed rings, L-shaped in radial cross-section and ofdissimilar materials, are attached to the edge of the piston, the oneelastomeric to contact the wall of the shell to consummate a gasimpermeable seal, the other supporting it mechanically, butcharacterized by relative flexibility horizontally but not vertically sothat the seal travels with the piston but accommodates itself to thecontour of the shell.

Preferably, but not necessarily, the shell ongaging foot of theelastomeric ring tapers in cross-section toward the shell wall to permita rocking action and the supporting ring for the elastomer. Specificallythe rigid portion of the foot of the support member or ring isrelatively thin, substantially perpendicular to the wall, andsufliciently flexible radially to conform to shell irregularity ordistortion. Preferably, but not necessarily, the supporting leg of theelastomeric ring depends from the piston so that the gas pressurepresses the foot outwardly into engagement with the Wall of the shell.Preferably, but not necessarily, this pressure is amplified by springpressure built into the supporting member to make it self-expanding,and, if desired, this characteristic may be utilized instead of, ratherthan in addition to, the gas pressure to provide the desired sealingload. Preferably, but not necessarily, the leg of the elastomeric ringis an annulus constituted by the gas impermeable elastomeric membranevertically stiffened by flat spring spacing members whether mounted onthe piston to supplement or oppose the gas pressure.

In summary, the feet of the superimposed rings constitute a reinforcedtapering sealing ring and the legs of the superimposed rings constitutea self-expanding, gas impermeable supporting diaphragm which dependsfrom the piston to take advantage of the pressure differential onopposite sides of it. Although each feature of the seal may each beutilized individually in holders of either the approximately or trulycircular type, the preferred and disclosed embodiment of the inventionincorporates all of them.

Having described my invention, I claim:

1. Sealing means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising, a plurality of flexible stavessupported adjacent the periphery of the piston in closely spacedrelationship and extending axially of the shell, a fulcrum ring in aplane between the upper and lower ends of the staves, said fulcrum ringbacking the staves, an elastomeric ring supported by the staves in aplane substantially parallel with but spaced from the fulcrum ring,means at the ends of the staves opposite the elastomeric ring flexingsaid ends inwardly and pressing the staves against the fulcrum ringwhereby the elastomeric ring is forced outwardly into sealing contactwith the shell, and a gas impermeable skirt joining the elastomeric ringwith the piston.

2. Sealing means'for a fluid storage reservoir of the shell and pistontype, said sealing means comprising, a plurality of flexiblestavessupportspaced relationship, said staves including foot portions turnedoutwardly toward the shell, an elastomeric ring supported by the footportions and engaging the shell in a plane substantially parallel withthe'pistonbut spaced downwardly therefrom, a gas impermeable skirtjoinin the elastomeric ring and the piston, a fulcrum ring on the pistonin a plane substantiall parallel with the elastomeric ring and backingthe staves between their upper and lower ends, and adjustable means atthe upper end of each stave flexing the stave inwardly against thefulcrum ring whereby the lower end of the stave is forced outwardlypressing the elastomeric ring into sealing contact with the shell.

. 3. Sealing means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising, a plurality of flexible stavessupported adjacent the periphery of the piston in closely spacedrelationship, an elastomeric ring supported by the staves in a planesubstantially parallel with the piston but spaced downwardly therefrom,said elastomeric ring disposed to the outside of the staves and incontact with the shell, an elastomeric bead extendin around the pistoninwardly of the staves and above the elastomeric ring, a flexible gasimpermeable skirt having its lower end sealed to the elastomeric ringand extending upwardly along the inner faces of the staves between thestaves and the elastomeric bead, and means flexing inwardly the upperends of the flexible staves whereby said skirt is pressed inwardly intosealing contact with the bead and said elastomeric ring is pressedoutwardly into sealing contact with the shell.

4. Sealing meansfor a fluid storage reservoir of the shell and pistontype, said sealing means comprising, a plurality of flexible stavessupported adjacent the periphery of thepiston in closely spacedrelationship and depending therefrom, said staves having foot portionsextending outwardly toward the shell in a plane substantially parallelwith the piston, an elastomeric ring supported by the foot portions andin contact with the shell, a fulcrum ring extending around the pistoninwardly of the staves and above th elastomeric ring, said fulcrum ringincluding an elastomeric bead and means mounting said bead, a flexiblegas impermeable skirt having its lower end sealed to the elastomericring and extending upwardly along the inner faces of the staves betweenthe staves and the elastomeric bead, and adjustable means flexininwardly the upper ends of the flexible staves whereby said skirt ispressed inwardly into sealing contact against the bead of the fulcrumrin and said elastomeric ring is pressed outwardly into sealing contactwith the shell.

5. Sealing means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising, a flexible gas impermeable annulussupported adjacent the periphery of the piston and extending axiallytherefrom, an elastomeric ring carried by the annulus disposed in aplane substantially parallel with the piston but spaced therefrom, saidelastomeric ring extending outwardly from the annulus and contacting theshell, means spaced from the elastomeric rin flexing the annulusinwardly and a fulcrum ring extending around the piston inwardly of theannulus and between the elastomeric ring and said means whereby theannulus is pressed inwardly into sealing contact with the fulcrum ringand the 10 elastomeric ring pressed outwardly into sealing contact withthe shell. f

6; Sealing means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising; a plurality of vertically disposedflexible staves supported by the piston adjacent to the peripherythereof in closely spaced side by side relationship, each of said staveshaving one portion thereof connected to said piston and having a freeend depending therefrom, a ring of elastomeric material carried by thefree ends of said staves in a substantially horizontal plane and aflexible ga impermeable skirt in sealed engagement with the piston andelastomeric ring,

said flexible skirt being disposed interiorly of said staves andpresenting a surface above said ring and below said piston to thepressure of the contents of said fluid storage reservoir, whereby fluidpressure on the inside-of the skirt is transmitted to the staves to urgesaid ring outwardly into sealing contact with the shell wall.

7. Sealing means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising, a plurality of vertically disposedresilient staves supported by the piston adjacent to the peripherythereof in closely spaced sideby side relationship, each of said staveshavingone portion thereof connected to said piston and having a free enddepending therefrom, a ring of elastomeric material carried by the freeends of said staves in a substantially horizontal plane and a flexiblegas impermeable skirt in sealed engagement with the piston andelastomeric ring, said flexible skirt being disposed interiorly of saidstaves and presenting a surface above said ring and below said piston tothe pressure of the contents of said fluid storage reservoir, wherebyfluid pressure on the inside of the skirt is transmitted to the stavesto urge said ring outwardly,

and means carried by said piston and engaging said staves for adjustablybending the resilient staves whereby the elastomeric ring is furtherspring urged outwardly into sealing contact with the shell wall.

8. Sealing means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising a plurality of vertically disposedflexible stave supported by the piston adjacent to the periphery thereofin closely spaced side by side relationship, each of said staves havingone portion thereof connected to said piston and hav ing a free enddepending therefrom, a ring of elastomeric material carried in ahorizontal plane below the piston by the free ends of the staves, and aflexible gas impermeable skirt in sealed engagementwith the pistonandthe elastomeric ring, said skirt having an inwardly disposed faceexposed to the pressure of the contents of said reservoir, whereby fluidpressure on the inside of the skirt is transmitted to the elastomericring to effect a sealing contact between said elastomeric ring and shellwall.

9. Sealing means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising a flexible gas impermeable skirt insealed engagement with the piston and depend-,

ing therefrom, an elastomeric ring joined in .sealed'relationship withsaid skirt and engaging l1 plane below said piston and in fixed verticalrelationship therewith whereby the fl'uid pressure on the inside of theskirt tends to expand said elastomeric ring outwardly against the shellwall to effect asealing contact between said ring and said 'wall. I r e-10. Sealing means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising a flexible gas impermeable skirt, asupport member including a plurality of vertically disposed stavescarried by said piston adjacent to the periphery thereof a ring ofelastomeric material supported bysaid staves in a substantiallyhorizontal plane, said elastomeric ring being of relatively flatconfiguration and having a U-shaped cross section, the outer edge of theelastofiieric ring constituting a tapered portion adapted to engage theshell in sealing contact, the inner portion of said elastomeric ringhaving an annular groove therein for mounting said ring upon saidsupport structure, said skirt and said elastomeric ring being in sealedengagement whereby said piston, skirt and elastomeric ring form with theshell a gas-tight enclosure of variable size.

l1. Sealing means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising a flexible gas impermeable skirtsecured to the margin of the piston, a plurality of vertically disposedstaves carried by said piston, a circular, radially expansible metalring supported by said staves in a substantially horizontal plane, aring of elastomeric material supported by the metal ring and havingsealed engagement with said skirt, said elastomeric ring having an outertapered portion engaging the shell in narrow band sealing contactwhereby said piston, skirt and elastomeric ring form with the shell agas-tight enclosure of variable size.

12. Sealing means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising a flexible gas impermeable skirtsecured to the piston, a circular, radially expansible metal ring, aplurality of staves secured to said piston and extending verticallytherefrom, said staves supporting said ring in a substantiallyhorizontal plane outwardly of said piston, a ring of elastomericmaterial having a tapered outer portion, said skirt and said elastomericring being in sealed engagement, said elastomeric ring having aninwardly disposed annular groove adapted to receive said metal ring andbe outwardly urged thereby into sealing contact with said shell.

13. Sealin means for a fluid storage reservoir of the shell and pistontype, said sealing means comprising a fiexible gas impermeable skirtsecured to the margin of the piston, a plurality of staves carried bysaid piston and extending vertically therefrom, a ring of elastomericmaterial supported by said staves in. a substantially horizontal plane,said elastomeric ring being of relatively flat configuration and havingan outer tapered portion engaging the shell whereby the 'shellcompresses said ring to form a narrow sealin contact band, said skirtand said elastomeric ring being'in sealed engagement whereby saidpiston, skirt and elastomeric ring form with the shell a gas-tightenclosure of variable size.

'1'4. Sealing means for a fluid storage'ifeservoir of the shell andpiston type, said sealing means comprising, a ilexiblegas impermeableskirt se cured to the piston and extending therefrom, .a circular,radially 'expans'ible metal ring, said metal ring comprising a fiatannular plate having radial slots therein, a plurality of verticallydisposed staves carried by said piston and supporting said ring in asubstantially horizontal plane outwardly of said piston, and a ring ofelastomeric material supported by thelmetal ring in sealing engagementwith'she'll wall, said elastomeric ring being joined to said skirt ingastight relationship whereby said piston, skirtand elastomeric ringform with said shell a gas-tight enclosure of variable size.

l5. Sealing means for a fluid storage reservoir of the shell and pistontype, said sealingmeans comprising a plurality of vertically disposedresilient staves mounted in closely spaced side by side relationshipadjacent to the periphery of the piston and supported thereby, each ofsaid staves having a free end spaced from the piston, a ring ofelastomeric material supported by the free ends of the staves in ahorizontal plane, a gas impermeable skirt joining the ring with thepiston and means carried by the piston and engaging each of said stavesat a point adjacent said piston for a'djustably imposing an outwardtension on the resilient staves whereby the elastomeric ring is springurged outwardly into sealing contact with the men wall.

16. Sealing means fora fluid storage reservoir of the shell and pistontype, said sealing means comprising a gas'impermeable skirt sec'u'redto'the margin of the piston, a plurality of vertically disposed stavescarried by'said piston, a circular expansible metal ring supportedbysaidstaves in a substantially horizontal plane, said metal ring comprisin afiat radially 'expansible member having a plurality of radial'sl'ots"therein, a

ring of'elastomeric material having aU-shaped cross section includin'ganannular groove at its inner-edge and a taperedportionterminating in anarrow-face at its outer edge,-said elastomeric ring being mountedcircumferentially on the support ring with the "support-ring engagingsaid groove and with the narrow -face' engagingthe shell in sealingcontact, -said-gas impermeable skirt and said-elastomericring'being insealed engagement whereby the piston, skirt and elastomeric ringformwith *the shell-a gas-tightenclosure of variable size.

EDWARD ".l. ARMSTRONG.

REFERENCES CI'11ED Thefoll'owing"references"are-of recordin the file ofthis-patent:

UNITED STATES PATENTS Number Name Date 1,924,029 Einbeck et al. Aug. 22,1933 2,371,966 Leise et a1. Mar. 20 1945 FOREIGN PATENTS Number CountryDate 473,314 Germany -'Jan. 7, 1926

